CS276014B6 - Process for preparing perfluoropolyethers with perfluoroalkyl or perfluorochloroalkyl terminal groups - Google Patents

Abstract

An improved process for preparing perfluoropolyethers having neutral end groups is disclosed, said process being based on the photooxidation of C₃F₆ and/or C₂F₄ and resulting in high yields of useful products, i.e. in products of controlled molecular weight, having perfluoroalkyl or perfluorochloroalkyl end groups.

Description

The invention relates to a process for the preparation of perfluoropolyethers having perfluoroalkyl or perfluorochloroalkyl end groups. These groups may contain one or two chlorine atoms.

It is known to produce perfluoropolyethers with perfluoroalkyl neutral end groups of photooxide fluoroolefins followed by fluorination under the action of fluorine gas in the presence of ultraviolet light, thereby obtaining peroxide group swelling and conversion of the terminal acid groups to perfluoroalkyl groups.

In this way, mixtures of the resulting products with different molecular weights and very broad molecular weight distributions are usually obtained. The proportion of high molecular weight products is usually substantial.

Methods of this type have been described in U.S. Patent Nos. 3,442,942, 3,665,041 and 3,683,027, and in European Patent Specification No. 4,902,027. EP 193,028.

For many industrial applications it is necessary to have available products and a relatively low molecular weight and higher homogeneity. Accordingly, there was a need to employ molecular weight reduction processes based on thermal catalytic fractionation of the product in the presence of the appropriate catalyst, as disclosed in European Patent Specifications Nos. 167,258 and 223,238.

This process is very important from an industrial point of view because it allows the full utilization of photooxidation products, which usually otherwise have a high average molecular weight and cannot be used directly effectively.

On the other hand, the separation of the relatively low molecular weight product and the crude mixture after photosynthesis is very complicated and difficult to perform on an industrial scale. In addition, the yield applicable to the low molecular weight product is very low, about 10 to 20%.

It would therefore be desirable to devise another industrial process that can produce high molecular weight products in the desired range directly in the photooxidation process without the need for subsequent molecular weight control steps.

The invention relates to a process for the preparation of perfluoropolyethers of the general formula

T-0 (C? ₂ CF ₂ O) _b / CF? CFO \ (C? ₂ 0) _p

where '

T represents a perhaloalkyl group optionally containing a chlorine atom, in particular one of the groups CTjY-, CFgYCEj-, YC? ₂ OF (CH 2) -, YC (CF 2) CF ₂ -, wherein Y represents a fluorine or chlorine atom,

R and B 'the same or different are fluorine or chlorine, m and n are from 0 to 20, p is from 0 to 40, and q is from 0 to 10, and when m = 0, n is 1 to 1 20 and p + q is from 0.01 to 0.5, when n = 0, q is also 0, m is in the range of 1 to 20 and the p / m ratio is in the range of 0.5 to 2, where n and m have a meaning different from 0, m + n is from 1 to 20 and the ratio p + q / m + n ranges from 0.01 to 0.05; limit values.

The process according to the invention is carried out in the following basic steps:

CS 276 014 B5

(a) Photooxidation of perfluoropropene and / or tetrafluoroethylene in the liquid reaction phase, consisting initially of C ^ F Fg and / or optionally a chlorofluorocarbon solvent and in the presence of fully halogenated ethylene 3 containing 1 to 4, 3 preferably 1 or 2 chlorine or bromine atoms, or iodine, by treatment with gaseous molecular oxygen under irradiation with ultraviolet light having a wavelength of 2 to 6 x 10 m, the liquid reaction mixture is maintained at a temperature of -20 to -100 ° C, preferably -50 to -60 ° C. Halogenated ethylene is fed to the reaction mixture simultaneously and with an oxygen stream in an amount of 50 mol%, based on perfluorolefins (Cyg and / or CiF4), usually in an amount not exceeding 20%. The halogenated ethylenes which can be used are, in particular, C? ₂ = OfCl, CFC1 = CFC1, oh? ₂ = CC1 ₂ or C? ₂ = CFBr.

b) Fluorination of the crude product obtained in step a) by treatment with fluorine gas at a temperature in the range of 100 to 250 ° C or 0 to 120 ° C while irradiating with ultraviolet light. This process is carried out in a manner known per se, as described, for example, in U.S. Patent Nos. 3,665,041 and 4,664,766. In addition to the conversion of acidic end groups to neutral perfluoroalkyl groups, substitution of all bromine and iodine atoms optionally present in the photooxidation product occurs. As for chlorine, substitution is very limited. In addition, the peroxide groups contained in the crude photooxidation product also decompose.

By the process according to the invention, it is possible to obtain in high yield fully fluorinated end products or products which contain only chlorine in the end groups. These products have high chemical and thermal stability and are fully comparable in their practical use to the known perfluoropolyethers with 3 perfluoroalkyl end groups. Thus, they can be used, for example, in the testing of electronic devices, for example in the heat shock test or in the component failure test according to European Patent Specification No. 203 348.

Another application of these substances is in the manufacture of lubricating materials according to U.S. Pat. No. 4,472,290.

The following examples illustrate the process according to the invention. Example 1 A) Photooxidation

In a 1000 ml cylindrical glass reactor, 2 ml light path, equipped with an internal coaxial silicon lining and a submerged tube for introducing gases with a cuff connected by 3 thermocouple to maintain the internal temperature and a reflux condenser maintained at -80 ° C at -60 ° C add 1600 g of C ^ ^Fg. ^A gas mixture of 27 liters / hr of molecular oxygen and 3 liters / hr of CgF2O4 was fed through the ^{TO10 / 10U} tube. The temperature of the liquid reaction mixture was maintained at -60 ° C throughout the cooling bath outside the reactor.

An ultraviolet light source (Hanau TQ 150) of 47 W ultraviolet radiation at a wavelength of 2 to 3 x 10? m, the source is switched on and the irradiation and supply of the reaction gases takes 5 hours.

After 5 hours of irradiation, the ultraviolet light source is turned off, the reaction mixture is degassed and the unreacted C ^ ^Fg is removed from the reactor by evaporation at room temperature. An oily polymeric residue is obtained. The product yield is 1.041 g. This residue is subjected to iodometric analysis to calculate an amount of active (peroxide) oxygen of 0.32% by weight, followed by NMR-F analysis to show that the residue consists of polyether type IV chains:

T - 0

n (CF ₂ O) _n (O) _T Y '(IV) where

.276 OM B6

T stands for any of the groups? CICFjCF-, C1CFCF ₂ -, or C1CF ₂ CF ₃ G? ₃ with the predominance of the first two types of end groups, Y 'means the groups:

-CF ₀ C <f.

^ά ^ FF while the second of these groups is present in an amount less than 5% of the end groups, m / n is very low (less than 0.05).

The viscosity of the product, determined at 20 ° C by a viscometer (Ostwald-Fenske), is 5.7 · Infrared analysis contains bands typical of the groups

(1884 cm -1)?

Mass spectrometry confirmed the presence of the end groups, set-NMR analysis, and the absence of units -CFC1CF ₂ -O- in the chain. NMR analysis showed that the m / n ratio was 0.01, the molecular weight was 960.

The chlorine content showed a chlorine content of 4.2% by weight.

Assuming that the resulting product should contain only one chlorine atom in the chain, as shown in the above formula, the average molecular weight of 840 was calculated.

The product was hydrolyzed with a stream of nitrogen saturated with water. After hydrolysis, the viscosity of the resulting product at 20 ° C was 31 x 10 ^-0 a / s. The hydrolyzed product was then distilled under vacuum at 2666-133 Pa at a maximum temperature of 210 ° C.

The fractions obtained and their properties are given in the following table:

Table 1

WITH molecular mass viakoeita x 10 nr / sec fraction I 130.6 400 4.8 fraction XI 23θ, 2 600 7.9 fraction III 552.3 1300 112

NMR- ¹⁹ F analysis was performed on all three samples and confirmed the structure where

(cf ₂₀ ) _o

T represents one of the groups CICFjCF-, C1CFCF ₂ - or CF _{3 3} ClCFgcf significant predominance of the first two types of end groups, and Y is -CFgCOOH, this analysis also allowed the calculation of molecular weight as indicated in Table 1.

B) Fluorination

CS 276 014 B5

In a 100 ml photochemical reactor equipped with a silicon mercury lamp jacket (Hanau TQ '50), a bubbler, a magnetic stirrer, a carbon dioxide trap and a saturated temperature control in both the reactor and the jacket were loaded using FC 70 ^ ®) and DOZ Galden @ ⁵ 'perfluorpolyetherkyseliny 210.2 g with a viscosity of 112.4 x 10 "nr / s zíekán material according to Example 1 fraction III. After the lamp was switched on, fluorination was carried out at a fluorine feed rate of 3 liters / h, maintaining the device temperature at 90 ° C.

After 6 hours the product obtained was completely neutral.

9

The structure was confirmed by N1IR P analysis on a sample of the final product

T - 0 C? ₂ CPO (CF ₂ O) - c? _3> where

T = YC? ₂ CP-, YCFCT ₂ - or YC? ₂ -, c? ₃ c? ₃ where

Y is fluorine or chlorine, and the ratio of end groups in which Y is chlorine to fully perfluorinated end groups is 0.96.

When fluorinating for an additional 20 hours, this ratio was changed to 0.53 to obtain fs?

189 g of the resulting product 3 with a viscosity of 19 x 10 m / a.

Photochemical fluorination carried out on fraction II of the sample obtained in Example 1 under the same conditions as above, but at 10 ° C, gave after 10 hours a completely neutral resultant product whose viscosity at 20 ° C was 1.5 x 10 6 / a , the product yield was 86%.

Example 2

A) Photooxidation of CjF ^ ⁺ = ^ 2

600 ml of a glass cylindrical reactor having a diameter of 80 mm and a volume of approximately 600 ml, equipped with an inner coaxial silicon jacket of 20 mm diameter, a submerged gas supply tube and a reflux condenser, maintained at -80 ° C, was charged 600 ml of A-12. ). A gaseous mixture consisting of oxygen, C ₂ F 4 and C ₁₅ F 15 is then fed into the reactor through a submerged tube and kept in the cooling bath outside the reactor to keep the liquid reaction mixture at the temperature indicated in Table 2 throughout the experiment. A lamp (Hanau TQ 150) with an output of 47 W of ultraviolet radiation at a wavelength of 200-300 nm was introduced into the silicon sheath, the bulb was switched on and the irradiation and the feed of the reactants took 5 hours.

The gases leaving the reactor were purged with an alkaline solution and then removed. After 5 hours, the lamp was turned off and the solvent was evaporated at room temperature to give an oily polymeric residue. This residue was subjected to iodometrioc analysis to determine the content of active oxygen and N14H ' F-analysis, which showed that the residue was composed of polyether type V chains:

Τ'- O (CF ₂ CF ₂ O) _n (C ₂ 0 0) _ffl (0) _y Y '(V), where

T 'is C1CF ₂ CF ₂ -, CICF ₃ - and

Y 'is -CF 8 OOOF, -COP.

The m / n ratio depends on the conditions of synthesis, in particular temperature, and ranges from 0.6 to 2.

CS 276 OH B6

The viscosity of the product was determined at 20 ° C by viscoaimetry (Ostwald-Penske). The results are shown in Table 2.

Table 2

try C. temperature (° C) o ₂ / c ₂ p ₄ c ₂ p ₄ / ctfe time (h) quantity of st (G) viscosity P. 0. (x. 10 ^_ ^ m ² / s) molecular mass ~ T '() 1 -40 2.37 9.3 5 Hl 11 2.8 1 470 '3 2 -40 2.35 11, 0 5 145 15.1 2.6 1 610 1.15. 3 -40 2.46 5.0 5 130 5.1 3.0 960 1.18 4 -60 3.5 19 Dec 5 163 40 2.5 2 700 1,2

values in a ratio of less than 1 indicate that some neutral end groups t 'have been replaced by acidic groups Y'.

B) Fluorination

Using a photochemical reactor, for example of the type described in Example 1 B) under the same conditions, but at 60 ° C, the product obtained according to Example 2 A) (Test δ. 4, Table 2) was fluorinated after hydrolysis of the peroxide groups. after heat treatment. The yield was 78%. After the fluorination, 12 hours was in 93% yield to obtain a product of The viscosity of 7 x 10 "^ m ² / s at 20 ° C, ¹ ^ P NMR analysis revealed that the polyether had the following structure:

T-0 (c- ₂ cp ₂ o) (c- ₂ o) -c? ₃ , where

T stands for YCF ₂ CF ₂ - or YCP ₂ - a

Y represents a chlorine or fluorine atom.

Example 3

A) Photooxidation using CPBr = C? ₂

In the photochemical reactor described in the example, with a charge of 800 g G ^ Pg, photosynthesis is carried out at -64 ° C with oxygen and BrC ₂ P _{3 being} fed in a submerged tube.

2.4: 1 at a total flow rate of 32 l / h, the components being fed separately diluted with helium. The reaction mixture is irradiated for 5 hours, then the lamp is turned off and the unreacted C18Pg is removed. 43.1 g of an oily product are obtained. Iodometric analysis showed 0.48% by weight of active oxygen.

The resulting product had a viscosity of 6.95 x 10 &lt; 4 &gt; m &^lt; ^{2 &gt;} / s, NMR analysis showed that the polyether consisted of a perfluoroether structure of the type

T-0 cf ₂ cpo (CP ₂ O) _and (0) _v - Y

CP.

where

T is BrOFgGF-, BrCFCPg- or CF 3cp ₃ cf _3, with a predominance of the two first group types, wherein Y is CPgCOF, or -COF, with a predominance of the first group type.

The molecular weight is 800, the m / n ratio is equal to 0.005.

T / Y ratio is 1, bromine analysis showed 8.9% ·

EN 276 014 36

Assuming that the resulting product contains only 1 bromine atom per molecule, the molecular weight is 898.

B) Fluorination

Using the same apparatus as in Example 1B), fluorination was performed at 5 ° C using a mixture of 20 g of the product obtained according to Example 3A) and 70 g of FG 70 [n (C ₁ F ₁ perfluortripentylamine) used. as a solvent.

After 19 hours of feed of 1 L / h of fluorine, 85.2 g of the resulting mixture was recovered from the reactor, from which 15 g of perfluoropolyether were separated by distillation. Peace ^? F-analysis showed that this perfluoropolyether consisted of a type structure

T-0

CCF ₂ O) _q - T which no longer contains peroxide groups and in which

T is one of BrCF ₂ CF-, BrCFCF 8, CF ₃ CF ₃ CF

CF 3 F 3 CF 3 -, CF 3 -, * 3

J> CF-, where the ratio between perfluorinated neutral end groups and neutral end groups 3 of bromine content is 3 ·

The resulting product was once again subjected to fluorination using the same reactor, but the experiment was carried out at 50 ° C with a fluorine feed of 3 L / h. After 40 hours of reaction, 19 g of a mixture were obtained, from which 11 g of perfluoropolyether were separated. MIR ^{7 by} F-analysis showed that this perfluoropolyether consisted of a t'-0 'cf ₂ cfo' (CF ₂ O) _n structure

T '

CF.

ιτα kde

T 'is -CF (CF ₃ ) ₂ , -CF ₃ CF ₃ CF ₃ -CF 4 and the molecular weight is 650.

In this experiment, a tube cooled to -80 ° C was placed at the exit of the reactor to catch reaction by-products which had a yellow color due to the presence of BrF and complexes thereof.

Claims (1)

PATENT CLAIMS A process for the preparation of perfluoropolyethers and perfluoroalkyl or perfluorochloroalkyl end groups of the general formula T-0 (CF ₂ C? ₂ O) _m / CF ₂ CFO \ (CF ₂ O) _p / 070 \ CFRR ' CF. where T represents a perhaloalkyl group optionally containing a chlorine atom, in particular one of the groups OF ₂ -, CF ₂ YC _{7 2} -, AOF 8 (CF ₃ ) -, TCF (C ₃ ) CF ₂ - in which Y represents a fluorine or chlorine atom; 7 EN 276 OH B6 R and J 'are the same or different, denote fluorine or chlorine, m and n are 0 to 20, p is 0 to 40, and q is 0 to 10, and when m = 0, n is 1 to 1 20 ap + q means numbers 0.01 to 0.5, if n = 0, q also means 0, m is in the range of 1 to 20 and the p / m ratio is in the range of 0.5 to 2, if n and m have a meaning different from 0, man is a number from 1 to. 20 and the ratio p + q / m + n ranges from 0.01 to 0.05, all the above-mentioned numbers are always understood including their limit values, characterized in that a) photo-oxidizing the perfluoropropene and / or tetrafluoroethylene in the liquid reaction phase, optionally using chlorofluorocarbons as the reaction solvent, by treatment with oxygen gas under irradiation with ultraviolet light at a reaction temperature of -20 to -100 ° C in the presence of fully halogenated ethylene containing 1 to 4, preferably 1 or 2, chlorine, bromine or iodine atoms, wherein the halogenated ethylene is added to the reaction mixture in an amount of up to 50 mol%, based on the amount of fluorolefin, (b) is carried out by fluorine treatment with fluorine gas at a temperature in the range of 100 to 250 ° C or 0 to 120 ° C while irradiating with ultraviolet light.